How To Choose A Home Solar Inverter? (The Ultimate Guide)

An important question when starting your home solar system

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When generating solar energy, most people think that it is all about solar panels. Although the panels are obviously the most important piece of equipment, there are many additional components that are crucial in a solar energy system.  

In fact, solar inverters are just as important as solar panels.  Choosing the right one can be quite difficult, as unfortunately, there is no one size fits all solution for solar power inverters.  

In this article, we will outline the purpose of an inverter, the different types of solar power inverters available on today’s market, and the things to consider when choosing your own inverter for a solar power system.  

Why Do You Need an Inverter for Solar Panels?

Photovoltaic (PV) solar panels harness the power of the sun in order to create usable energy.  Whenever the light shines on a solar panel, the electrons become active and generate Direct Current (DC) electricity.  Most homes use Alternating Current (AC) electricity to power plug-in devices like lamps, microwaves, phone chargers, etc.

So, in order to use the DC electricity generated by the solar panels, you will need an inverter to convert the current into usable AC electricity.  

The Different Types of Solar Power Inverters

Every year, innovators continue to push renewable energy forward with new solar technology.  Currently, there are three main types of power inverters designed specifically to create the most usable electricity from solar power:  traditional string inverters, string inverters with power optimizers, and microinverters.  

Traditional String Inverters

String inverters, also known as centralized inverters, are the most popular choice for solar inverters in the world.  They are also the most cost-effective option for most residential solar panel installations.  

String inverters have been used for decades.  They work by connecting a series of solar panels in a group or “string.”  It is not uncommon for large inverters to have several strings of solar panels in a large installation.

Although they are the least expensive type of solar inverter, there is one major downside to using a string inverter.  When panels are connected in a series, the system will only be able to generate electricity at the rate of the solar panel with the lowest amount of output.  

This means that if one of your solar panels is damaged or blocked by the shade of a tree or building, then the entire string of panels that it is connected to will generate less electricity than usual.  

For this reason, most solar panels that are placed on a string inverter are usually arranged to be facing the same direction with an equal amount of sunlight per day.  Solar panels also rarely break or require maintenance, so there is not as much risk associated with a string inverter as may be imagined. 

String Inverters Power Optimizers 

In order to combat the fact that solar panels on string inverters are only as powerful as the weakest panel, some solar energy systems use power optimizers to increase electricity production efficiency.

Power optimizers are used to detect and release solar power from each individual solar panel.  They are usually found on the underside of a solar panel.  By optimizing the electricity at the panel level, and then sending that energy to the string, power optimizers enable for more electricity to be produced if a panel is not working at its highest capacity.

Adding power optimizers to a string inverter will obviously cost more money than a traditional solar energy system.  However, if your solar panels are subject to varying amounts of shade throughout the day, then adding power optimizers may be a very cost-effective option for maximizing your solar energy production and usage. 

Microinverters 

The third and most expensive type of common solar inverter is actually a series of smaller microinverters.  Microinverters are a Module Level Power Electronic (MLPE), just like a power optimizer, because it is usually found directly on the solar panels themselves.

Rather than regulating and optimizing the DC current from each panel, microinverters actually convert the electricity to an AC current directly after it is harnessed from the sun.   

Microinverters are generally much more expensive than traditional string inverters or power-optimized systems, but they are still very popular because of the added benefits they provide.

By converting the power directly onsite, each solar panel works as an individual part of the overall solar production, rather than as a unit along a string.  If one panel is shaded, it will produce as much solar electricity as it can, but will not reduce the output of its neighboring panels like in that of a string inverter. 

With a microinverter, you are also able to monitor the individual performance of each solar panel more closely, which allows you to quickly identify possible damages or defects.  

The Difference Between “Sine Waves” and “Modified Sine Waves”

When exploring different solar inverter options, you are likely to come across both “sine wave” and “modified sine wave” options.  Although this language may seem technical, the decision on which technology to choose is quite easy. 

Modified sine waves, also referred to as modified square waves, are cheaper, but less efficient in converting DC power to AC power.  The electricity produced in a modified sine wave is choppy and inconsistent. Because of this, sine wave inverters are much better for residential solar energy systems. 

A sine wave inverter will be able to deliver the best possible electricity to the grid.  Sine wave inverters are often referred to as “true” or “pure sine waves” in order to convey a low level of distortion associated with the electricity.  

How to Choose the Best Solar Inverter 

When determining the best solar inverter for your home’s solar energy system, there are three main factors that will influence your choice.  You will need to identify the type, size, and brand that combine to make the best solar inverter for your individual needs. 

Choosing Your Preferred Type of Power Inverter

As outlined above, there are three main types of power inversion systems for solar energy:  traditional string, string with power optimizers, and microinverters. Choosing the right type of inverter is determined by your budget and potential energy production. 

If you have the luxury of a solar panel system that receives the same amount of sunlight throughout the day (i.e. all on the same roof face with no tree coverage), then a traditional string inverter is usually the best choice, as it will be the most affordable.

If your system receives various amounts of sunlight throughout the day, then you may want to add a “smart module” such as power optimizers or microinverters to prevent your panels from not producing as much electricity as they are able.  

When it comes to choosing between power optimizers on a string inverter or a series of microinverters, the choice usually comes down to budget.  Power optimizers are usually viewed as the nice halfway point between the cost of a traditional string inverter and a microinverter system.

Microinverters are the most expensive option but certainly come with enough included benefits to be a popular choice.  Because microinverters allow solar panels to work completely independently of each other, they allow for the most efficient overall production

Additionally, if the inverter on a string system (with or without power optimizers) were to break down or malfunction, then all power generated would be lost.  If one of a series of microinverters were to break, it would not prevent the rest of the solar panels from producing usable solar electricity.  

In a remote area in which parts could not be easily fixed or replaced, choosing a series of microinverters would be the best option to minimize the potential loss of power production.  

Choosing The Right Size for your Solar Inverter

The size or capacity of your solar inverter is completely dependent on the maximum input of electricity generated by your solar panels.  

Solar electricity is measured in watts (W) or in the case of larger systems, kilowatts (kW), which are equal to 1000 watts.  Solar panels are rated at a DC capacity and generally range in size from around 50 to 400 watts. Most residential solar panels are around 300 watts, but new technologies are developed each year.

To calculate the total size of your solar energy system, simply multiply the number of panels by their rated capacity.  If your solar array consists of twenty 200 watt solar panels, then you have a 4 kW (or 4000 watt) system. In this case, you will want to install an inverter that is rated with a minimum 4000 watt capacity.

Generally speaking, it is almost always a good idea to leave room for error and choose an inverter that is sized at a slightly higher capacity than your solar array.  This way, if your system is producing more energy than estimated, you will have a continuous flow of power that will not damage the inverter. 

In the case of microinverters, the size and capacity of each microinverter will directly correspond to the solar panel to which it is affixed, rather than the total wattage of the entire system.  Some microinverters are specifically designed for certain solar panels, but the same advice for having a bit of extra capacity still applies to each unit.  

Choosing the Right Brand and Model Solar Inverter

Once you’ve decided on the type and size of your inverter, finding the best solar inverter for your electricity needs will come down to a few main decision drivers.  Most importantly, you should consider the manufacturer’s reputation, inverter warranty, and overall performance.

Most solar inverters live their life outside battling the elements to generate clean, renewable energy.  For this reason, and due to their constant daily performance, inverters are one of the most common parts of a solar energy system to break or malfunction.

In the case of a downed inverter, you will want to have both a warranty to cover the costs of the damage and the ability to contact a company that will be able to quickly replace the part.  

Lifespan and Performance

The average lifespan of a high-quality solar inverter is around 10 years.  If the warranty of a product is not close to that figure, then you will want to shy away from it.  An inverter can be a large investment, so you will want to be sure it is insured to operate for at least a decade.

Secondly, it is also a really good idea to research and try contacting the customer service of the manufacturer.  If your inverter (or microinverter) were to malfunction, then you will be going without solar electricity generation until the problem is fixed.  Going for weeks without having a repairman or fresh inverter will leave you with functionless solar panels and increased dependence on the utility grid.

Lastly, the daily performance of your inverter is one of the most important factors to consider when choosing the best inverter for your solar electricity system.  Unfortunately, energy is lost while converting the electricity from DC to AC, so the efficiency of your inverter will determine the actual amount of usable electricity generated by your system.  

Power Monitoring

In order to minimize the power loss, you will want to compare efficiency ratings between your possible options.  It is important to review both the peak, average, and low-efficiency ratings as your solar panels will be receiving various amounts of sunlight per day.

In order to measure the daily performance of your solar panels, a system for monitoring electricity generation will need to be installed.  Many top tier solar inverters come with an easy monitoring system directly on the device or connected through WiFi or Bluetooth to a phone or computer.  

Being able to see your daily production is the best way to ensure the maximum system efficiency of your solar panels by being able to see defects as soon as they arrive.  You will also be able to brag to your friends and neighbors about how your rooftop power plant is performing.

With so many sizes and types available on the market, the process of choosing a solar inverter can be quite stressful for both a first-time or experienced buyer.  We hope this article was helpful in both explaining the role of an inverter and what to look for when finding the best inverter for the solar panels on your home.  

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